1. Field of the Invention
The present invention relates generally to charge pump circuits, and in particular to charge pump circuits that provide a regulated output voltage.
2. Discussion of the Related Art
A charge pump circuit is generally used for boosting a power supply voltage to a higher voltage level to be used for powering ancillary circuits. Closed loop control is sometimes used with charge pumps to provide a regulated output voltage. However, charge pumps that include closed loop control typically have extremely slow response times due to the relatively small amount of energy that can be transferred during each clock cycle.
The present invention provides a circuit and method having a fast response time for generating a regulated voltage from a first voltage of a first voltage source. The circuit includes a driver for generating a drive signal. The driver includes a clock input for receiving a clock signal. A charge pump that has a first voltage input coupled to the first voltage source. In response to the drive signal, the charge pump provides a pump voltage that is boosted from the first voltage. An amplifier has a reference input coupled to a reference voltage, a sense input coupled to a sense signal representative of the pump voltage, and an output. The amplifier is operable in response to a difference between the reference voltage and the sense signal, to control the driver. A switch is coupled from the amplifier output to an output of the charge pump such that the pump voltage is controllably boosted by the amplifier output through the switch.